Bicyclic amidine-copper salt catalyzed polyarylene ether formation



United States Patent U.S. Cl. 260-47 8 Claims ABSTRACT OF THE DISCLOSURE Process for the production of polyarylene ethers in inert solvents from 2,6-disubstituted phenols by oxidative coupling with oxygen, characterized in that the oxidative coupling is carried out in the presence of a catalyst system of copper salts and bicyclic amidines of the general formula wherein R denotes an alkylene radical having 2-4 carbon atoms and R is an alkylene radical which may contain a further tertiary nitrogen atom.

This invention relates to a process for the preparation of polyarylene ethers from 2,6-disubstituted phenols by oxidative coupling using oxygen.

It is already known that 2,6-disubstituted phenols can be reacted to form polyarylene ethers in inert solvents with oxygen in the presence of a catalyst system consisting of copper salts and tertiary amines, preferably pyridine derivatives. In order to obtain high molecular weight products, however, a large molar excess of the tertiary amine is necessary. Catalyst mixtures for obtaining polyarylene ethers which have been described in the literature, for example, contain about 100 moles of pyridine per mol of copper salt. Polyarylene ethers prepared in this way contain nitrogen in quantities of 0.1 to 0.5% by weight. Stability and colour of these polymers are alfected thereby in an undesirable manner. Furthermore, the process is rendered much less economical since the quantity of catalyst is usually greater than the quantity of the 2,6-disubstituted phenol which is to be oxidised. If the oxidative coupling of 2,6-disubstituted phenols is carried out, however, in the presence of catalyst mixtures with a molar ratio of copper salt to pyridine of 1:10 or less, 3,5,3',5'-tetra-substituted diphenoquinone as the main product is obtained. Furthermore, it was found that 2,6-disubstituted phenols undergo oxidative coupling in inert solvents to produce polyarylene ethers by using a catalyst system of copper salts and primary or secondary amines.

It has now been found that high molecular weight polyarylene ethers of the following general formula 3,442,885 Patented May 6, 1969 ice wherein R denotes a lower alkyl radical and x an integer, can be prepared in high yields in inert solvents from 2,6- disubstituted phenols by oxidative coupling with a catalyst system of copper salts and bicyclic amidines of the following general formula:

R denotes an alkylene radical containing 2 to 4 carbon atoms and R an alkylene radical which may contain a further tertiary nitrogen atom.

Examples of these amidines are, for example, bicyclic Examples of 2,6-disubstituted phenols suitable for use in the oxidative coupling are 2,6-dimethylphenol and 2,6- diethylphenol and mixtures thereof.

To carry out the process of invention, the catalyst system consisting of copper salt and bicyclic amidine is dissolved or partly dissolved and partly suspended in an inert solvent. Then the 2,6-disubstituted phenol is added to the catalyst solution and the oxidative coupling to form the polyarylene ether is carried out by introducing oxygen into the reaction solution. The exothermic reaction causes a considerable rise in temperature in the reaction solution. The end of the reaction is indicated by a drop in the reaction temperature. It is advisable to continue the introduction of oxygen for some time thereafter to make sure that the reaction is completed. In order to obtain high molecular weight products, the oxidative coupling should be carried out at temperatures between 15 and 60 C.; therefore in some cases it is advisable to add only a part of the 2,6-disubstituted phenol to the reaction solution. The residual amount is added in portions during the processing of the reaction, or to adjust the reaction temperature to a particular level by means of a thermostat. Furthermore, it is advantageous to trap the water set free in the oxidative coupling to form polyaryl ethers by addition of water binding agents such as MgSO, or Na SO The resulting polyarylene ethers are isolated by precipitating their solutions into acidified nonsolvents. The solid materials are separated for further purification. Solvents for carrying out the reaction are systems which dissolve the polyarylene ethers, for example aromatic and araliphatic hydrocarbon, preferably benzene. Furthermore, a small proportion of this solvent may be replaced by ketones or alcohols without significantly disturbing the process.

vThe components used for the catalyst mixture are bicyclic amidines already mentioned above and copper salts of hydrochloric acid, hydrobromic acid, sulphuric acid, nitric acid, and aliphatic carboxylic acids such as acetic acid. Cuprous chloride is preferred. In order to obtain high molecular weight polyarylene ethers, the molar ratio of copper to phenol in the reaction solution may be varied within wide limits. Molar ratios of between 1:40 and 1:250 are preferred. The molar ratio of copper to bicyclic amidine, on the other hand, should generally not be greater than 1:10 and preferably should lie between 1:2 and 1:3, since at higher copperzamidine ratios the quality of the crude polymers is usually impaired. It is not essential to use pure oxygen when carrying out the oxidative coupling of the 2,6-disubstituted phenols; mixtures of oxygen with inert gases may be used also in the form of, for example, air or mixtures of magnesium sulphate, 1.35 parts by weight of bicyclic amidine of the formula oxygen with noble gas. 5

The P Y Y ethers P P to lnven and the quantity of copper salt indicated in the table tron are drstlngulshed by then desirable mechanical, therb The molar ratio f ZGdimethYLPhenol to Coppgr mal and elecfl'lcal P P T y can be Worked P Into salt is in each case 82:1 and the molar ratio of copper moulded articles by the il'lJECilOn moulding process and l to bi i i i 1:22 f011S, fi1ameI1t$ and coatlflgs can be Produced from then In order to isolate the resulting polyarylene ether, the SOIUUOIIS- solid constituents are removed from the reaction solu- Thqfollowmg examples illustrate more speclfically the tion b filtration. About 500 parts by volume of benzene lllventlonare then removed from the solution by distillation at re- Examples 1-6 15 duced pressure. The polymer is precipitated by pouring 30 parts by weight of anhydrous magnesium sulphate the remainlng solutlon into 1000 parts by volume of v methanol and 10 parts by volume of concentrated byand, as catalyst, the desired quantity of anhydrous drochloric acid and is Se armed b filtration cuprous chloride and bicyclic amidine in the molar ratio p y of about 1:2 are introduced into 500 parts by volume of anhydrous benzene in a 4-necked flask equipped with Copper Salt Reaction Yield stirrer, thermometer, reflux condenser and gas inlet tube. Parts b temp eraparts by After the addition of 50 parts by weight of 2,6-dimethyl- Fmulfl fight weight phenol, dry oxygen is introduced into the stirred reaction 7 S04 0.80 20-38 46. 1. 315 solution at a temperature of 23 C. upwards. The tem-' 25 3 f gg 313g 2%? 33:; {3 perature at first rises and may reach about 40 C. depend- 10---- C11( 3COO)Z-H2o 1. 00 20.32 45.4 1. 480 ing on the catalyst mixture, catalyst quantity and velocity of flow of the stream of oxygen. To complete the oxida- Example 11 tive coupling, introduction of oxygen is continued for minutes after lowering of the reaction temperature. 30 b 32? gi s; 2:8 2 f i z g g g g The polyarylene ether produced is precipitated by f th f. i 1 G 0 f f n par S y pouring the reaction mixture into 1000 parts by volume w 1g 0 6 my 0 m1 6 0 e Ormu a of methanol and 10 parts by volume of concentrated N hydrochloric acid. The precipitated product is filtered off, washed with methanol and freed from salts adhering 35 N to it by washing it with water (see Table I).

TABLE I CuCl, Highest Yield, parts Parts reaction parts by by temperaby Ex. weight Formula weight ture, 0. weight i.

N a 0.5 M

N N0Hi 1.84 33 43.1 1.45

The relative viscosity nmh was, in all examples, measand 50 parts by weight of 2,6-dimethyl-phenol are placed ured at 20 C. at a concentration of 1 g. of polyarylene in the apparatus used in Examples 1-6. ether in 100 ml. of chloroform. (a) Oxygen is introduced with stirring at 22 C. The E 1 7 10 reaction temperature rises to 41 C. over about 2 hours. Xamp es When the temperature has dropped again, the polyaryl- Oxygen is passed in accordance with the instructions ene ether is precipitated by pouring the reaction mixture given in Examples 1-6 through a reaction mixture of into 1500 parts by volume of methanol and 10 parts by 1000 parts by volume of benzene, 50 parts by weight of volume of concentrated hydrochloric acid.

2,6-dimethyl-phenol, 40 parts by weight of anhydrous Yield: 45.1 parts by weight; m 1.65.

(b) 30 parts by weight of magnesium sulphate are added to the reaction solution and the procedure described under 11 (a) is carried out. Residues of salt are Washed out of the polymer with water.

Yield: 48.5 parts by Weight; w 3.602.

(c) 40 parts by weight of anhydrous sodium sulphate are added to ehe reaction solution and the procedure described under 11 (a) is carried out.

Yield: 45.8 parts by weight; 1 1.81'5.

(d) 30 parts by weight of magnesium sulphate are added to the reaction solution, and air is passed through for about 8 hours with stirring. The reaction temperature rises from 20 to 26 C. in about 3 hours. The polymer is isolated by the method described in Example 11 (a).

'Residues of salt are Washed out with Water.

Yield: 44.2 parts by weight; m 2.76.

Example '12 Using the apparatus described in Examples 1-6, 0.2 part by weight of anhydrous cuprous chloride and 0.5 part by weight of the bicyclic amidine of the formula are (a) dissolved in 500 parts by volume of toluene. 50 parts by weight of 2,6-dimethy-lphenol are then added to the reaction solution and air is passed through the solution for 7 hours. The temperature rises from 22 to 32 C. during the reaction time.

The polyarylene ether is precipitated by pouring the reaction solution into 1000 parts by volume of methanol and 10 parts by volume of concentrated hydrochloric acid.

Yield: 40.5 parts by weight; n 1.31.

(b) dissolved in 500 parts by volume of benzene. 50

parts by weight of 2,6-dimethylphenol are then added to the reaction solution and the reaction is from then on carried out using the procedure of 12 (a).

Yield: 42.1 parts by weight; 11ml, 1.41.

Example 13 Using the apparatus described in Examples '1 to 6, 50 parts by weight of 2,6-diethylphenol and 40 parts by weight of anhydrous magnesium sulphate in 1000 parts by volume of benzene are gasified with oxygen for 3.5 hours, anhydrous cuprous chloride and the bicyclic amidine of the formula being used in the molar ratio of 1:2 or 2.2 as catalyst.

500 parts by volume of benzene are distilled olT in vacuo and the polyarylene ether formed is precipitated from the remaining solution by pouring it into 1000 parts by volume of ethanol and 10 parts by volume of concentrated acid.

(a) 0.2 part by weight of cuprous chloride and 0.5 part by weight of amidine are used as catalyst. Reaction temperature 22-28 C.

Yield: 40. 6 parts by weight; 1 1.41.

(b) 0.5 part by weight of cuprous chloride and 1.36 parts by weight of amidine are used as catalyst. Reaction temperature 22 to 32 C.

Yield: 43.1 parts by weight; n 1.46.

wherein R denotes an alkylene radical having 24 carbon atoms and R is an alkylene radical which may contain a further tertiary nitrogen atom, and in an inert organic solvent at temperatures between 15 and "60 C.

2. Process according to claim 1, characterized in that the catalyst contains the copper and bicyclic amidine in a molar ratio 0512-2 to 1:3.

3. The process of claim 1 wherein the bicyclic amidine has the formula 4. The process of claim 1 wherein the bicyclic amidine has the formula N C N 5. The process of claim 1 wherein the bicyclic amidine has the formula N Q N 6. The process of claim 1 wherein the bicyclic amidine has the formula 7. The process of claim 1 wherein the bicyclic amidine has the formula 8. The process of claim 1 wherein the bicyclic amidine has the formula References Cited UNITED STATES PATENTS 3,306,875 2/1'967 Hay 260-47 3,313,776 4/1967 Borman 26047 WILLIAM H. SHORT, Primary Examiner. M. GOLDSTEIN, Assistant Examiner. 

